I have always had irregular periods but the last two months I have been on time. This month I haven't gotten my period, but I have NO pregnancy symptoms and got a negative result on a First Response at home pregnancy test a day after I expected my period. I have had sex multiple times during the last month, possibly during a time when I could be ovulating only using the pull out method (ALWAYS correctly though). Is it possible that I'm pregnant?

There is no correct way to do the pull out method. You put unprotected Penis in Fertile woman and baby can occur. There is far more sperm in pre-ejaculate then is necessary for you to become pregnant. You should use something a lot more effective when trying to prevent pregnancy. Condoms at the very least.

That aside. It is entirely possible that you're pregnant. It is also entirely possible that your period is irregular again. If your period has a history of being irregular, you can't expect it to suddenly become regular. Take another test in a week or two if you don't get your period.

Also, use better protection.

ANY time there is penile insertion there is the risk of pregnancy. You can reduce the risks, but not eliminate them. And the pull out method is the most ineffective way to reduce the risks.

Taking at test one day after your period is due is also not effective. The accuracy of these tests increases greatly so that 95+% accuracy is achieved about 2 weeks after your missed period.

If pregnancy scares you, then why are you taking such risks?